SLURRY SEPARATION SYSTEM

Abstract

A system and method effect the separation of wax and oil from a sorghum slurry. The sorghum slurry is mixed with supercritical CO.sub.2 to create a first output, and the first output is mixed with liquid CO.sub.2 causing a sudden drop in temperature such that solid wax particles drop from the first output to create a second output of CO.sub.2 and oil. The second output is heated while reducing pressure such that the CO.sub.2 is put into a gas phase and the oil separates from the CO.sub.2.

Claims

1. A system for separating wax and oil from a sorghum slurry, the system comprising: a slurry supply tank heated to a temperature equal to or above a melting temperature of sorghum wax; a CO.sub.2 supply tank storing CO.sub.2 in liquid phase; a slurry line from the slurry supply tank including a first pump and a first heat exchanger; a CO.sub.2 line from the CO.sub.2 supply tank including a second pump and a second heat exchanger, the second pump and the second heat exchanger are configured to put the CO.sub.2 into a supercritical state; a dissolving chamber receiving output from the slurry supply tank via the slurry line mixed with the supercritical CO.sub.2 via the CO.sub.2 line; a precipitation chamber receiving output from the dissolving chamber mixed with CO.sub.2 in liquid phase from the CO.sub.2 supply tank, wherein the CO.sub.2 in liquid phase solidifies the wax and separates the wax from the slurry such that the wax precipitates by gravity to a bottom of the precipitation chamber; an output line from the precipitation chamber through which a mixture of CO.sub.2 and oil flow, the output line including a third heat exchanger that is configured to heat the mixture and a flow regulator that is configured to reduce pressure in the output line; and a separation chamber receiving CO.sub.2 and oil from the output line, wherein the CO.sub.2 is in a gas phase, and wherein the oil separates from the CO.sub.2.

2. A system according to claim 1, wherein the CO.sub.2 line from the CO.sub.2 supply tank comprises a sub-line, the system further comprising a fourth heat exchanger on the sub-line that cools the CO.sub.2 to a temperature below 0 degrees C., the sub-line mixing with the output line ahead of the precipitation chamber.

3. A system according to claim 2, further comprising a third pump on the sub-line.

4. A system according to claim 2, wherein a ratio of the CO.sub.2 to the output from the dissolving chamber is at least 7:1.

5. A system according to claim 1, further comprising a return line that carries CO.sub.2 from the separation chamber, the return line including a fifth heat exchanger that cools the CO.sub.2 from gas phase to liquid phase.

6. A system according to claim 1, wherein a ratio of the supercritical CO.sub.2 from the CO.sub.2 line to the slurry in the slurry line is at least 6.14:1.

7. A method of separating wax and oil from a sorghum slurry, the method comprising: (a) inputting a mix of the sorghum slurry and supercritical CO.sub.2 into a dissolving chamber; (b) separating the wax from the sorghum slurry in a precipitation chamber by mixing output from the dissolving chamber with liquid CO.sub.2; and (c) heating output from the precipitation chamber such that the CO.sub.2 is in a gas phase, thereby separating the oil from the CO.sub.2 in a separation chamber.

8. A method according to claim 7, further comprising storing the sorghum slurry in a slurry supply tank at a temperature above a melting point of the wax and at a predetermined pressure, and storing liquid CO.sub.2 in a CO.sub.2 supply tank, wherein step (a) is practiced by outputting the sorghum slurry from the slurry supply tank and by outputting the CO.sub.2 from the CO.sub.2 supply tank.

9. A method according to claim 8, wherein the predetermined pressure is 700-1400 psi.

10. A method according to claim 8, further comprising, prior to step (a), heating and pressurizing the liquid CO.sub.2 into the supercritical CO.sub.2.

11. A method according to claim 7, further comprising, prior to step (b), outputting liquid CO.sub.2 from a CO.sub.2 supply tank to a heat exchanger to cool the CO.sub.2 to a temperature below 0degrees C., wherein the liquid CO.sub.2 in step (b) comprises the cooled CO.sub.2.

12. A method according to claim 7, wherein step (b) further comprising collecting solid wax particles in the precipitation chamber, and melting the solid wax particles for retrieval via a wax drain.

13. A method according to claim 7, wherein step (c) comprises heating the output from the precipitation chamber and reducing a pressure such that the CO2 is in the gas phase.

14. A method according to claim 13, further comprising draining the oil from the separation chamber.

15. A method according to claim 7, further comprising, after step (c), cooling the CO.sub.2 to be in a liquid phase, and returning the CO.sub.2 to a CO.sub.2 supply tank.

16. A method according to claim 7, wherein step (a) is practiced such that a ratio of the supercritical CO.sub.2 to the sorghum slurry is at least 6.14:1.

17. A method according to claim 7, wherein step (b) is practiced such that a ratio of the liquid CO.sub.2 to the output from the dissolving chamber is at least 7:1.

18. A method of separating wax and oil from a sorghum slurry, the method comprising: mixing the sorghum slurry with supercritical CO.sub.2 to create a first output; mixing the first output with liquid CO.sub.2 causing a sudden drop in temperature such that solid wax particles drop from the first output to create a second output of CO.sub.2 and oil; and heating the second output while reducing pressure such that the CO.sub.2 is put into a gas phase and the oil separates from the CO.sub.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] These and other aspects and advantages will be described in detail with reference to the accompanying drawing, in which:

[0021] FIG. 1 is a schematic diagram of the slurry separation system according to the described embodiments.

DETAILED DESCRIPTION

[0022] With reference to the drawing, the system 10 includes a slurry supply tank 12 heated to a temperature equal to or above a melting temperature of sorghum wax. With the melting point of the sorghum wax at 83 degrees C., the slurry supply tank may be heated to a temperature around 93 degrees C. up to 215 degrees C. Above 215 degrees C., the wax may burn or become discolored.

[0023] The slurry supply tank 12 may be maintained at pressures between 700-1400 psi. The pressure enables the tank to feed a downstream pump. If the pressure is too low, the downstream pump will be inefficient. Pressures above 1400 psi pose safety risks and add substantial costs.

[0024] A CO.sub.2 supply tank 14 stores CO.sub.2 in liquid phase. In some embodiments, the CO.sub.2 may be stored at 4 degrees C. at a pressure around 1000 psi. The CO.sub.2 at 4 degrees C. keeps the CO.sub.2 dense enough in liquid phase to make it efficient while maintaining economic feasibility. Temperatures below 11 degrees C. could cause the oil to solidify, which is undesirable. Temperatures above 12 degrees C. will significantly slow the process.

[0025] The CO.sub.2 supply tank 14 may include top-mounted valves enabling removal of nitrogen or oxygen should they get into the system.

[0026] A slurry line 16 from the slurry supply tank 12 includes a first pump 18 (i.e., the downstream pump discussed above) and a first heat exchanger 20. The first pump 18 raises the pressure in the line 16, and the heat exchanger 20 raises the temperature in the line 16. The pressure and temperature are set to dissolve all wax and oil components of the sorghum slurry.

[0027] A CO.sub.2 line 22 from the CO.sub.2 supply tank 14 includes a second pump 24 and a second heat exchanger 26. The CO.sub.2 may be passed through one or more check valves. The second pump 24 and the second heat exchanger 26 function to elevate the CO.sub.2 into a supercritical state. The CO.sub.2 solvent is in a continuous loop being pumped from a storage pressure/temperature in liquid phase in the CO.sub.2 supply tank 14 to a dissolving temperature/pressure in a supercritical state. In an exemplary embodiment, the wax and oil components in the slurry are dissolved in supercritical CO.sub.2 at 10,000 psi and 93 degrees C. Higher pressures increase safety concerns and would affect the price of the machinery. Lower pressures (e.g., below 6,000 psi) would not push enough throughput for economical operation.

[0028] A dissolving chamber 28 receives output from the slurry supply tank 12 via the slurry line 16 mixed with the supercritical CO.sub.2 via the CO.sub.2 line 22. That is, slurry (composed of oil and wax) is heated to a temperature above the wax melting point and is passed through a pump pressurizing the slurry, e.g., to 10K psi. The slurry passes through a check valve and is injected into the dissolving chamber 28 at a rate that ensures that the slurry is continuously and completely dissolved. In some embodiments, the slurry is injected into the dissolving chamber 28 at a rate of at most 14% of the total CO.sub.2 slurry stream by volume, with the other 86% of the stream being comprised of CO.sub.2. This is thus at least a 6.14:1 ratio between the CO.sub.2 and slurry volumes, respectively. If the ratio is increased resulting in an increased amount of slurry, it would be difficult if not impossible to dissolve at this pressure. An increased ratio could be successful with higher pressure, enabling the system to throughput more slurry.

[0029] The CO.sub.2 stream and slurry stream may also merge outside the dissolving chamber 28 and then enter the dissolving chamber 28 together as shown in the drawing. The dissolving chamber 28 endeavors to accomplish two things. First, the dissolving chamber 28 allows time for the slurry to be dissolved completely into solution. Second, if a slurry component does not dissolve, it gives a location for this insoluble material to sit and not be carried over into the downstream process components.

[0030] The colliding or mixing point outside the dissolving chamber 28 allows for the insertion of perforated, sintered, porous, or other types of screens or mixing devices at this location and downstream of it to assist with dissolution. For reference, this is different from current state-of-the-art designs that use a batch method. This method also allows the system to scale up to any rate of slurry production, preventing the described system from being a bottleneck in production.

[0031] In some embodiments, the dissolving chamber 28 may include a heater (not shown) in case of component shut down or to maintain elevated temperatures.

[0032] A precipitation chamber 30 receives output from the dissolving chamber 28 mixed with CO.sub.2 in liquid phase from the CO.sub.2 supply tank 14. A sub-line 32 from the CO.sub.2 supply tank 14 includes a pump 34 that increases the pressure in the sub-line 32 and a heat exchanger 36 that cools the CO.sub.2 to a temperature below 0 degrees C. In some embodiments, the heat exchanger cools the CO.sub.2 to 20degrees C. The sub-line 32 may also include a flow regulator valve 38 to control CO.sub.2 flow. The CO.sub.2 in the sub-line 32 mixes with material in the output line from the dissolving chamber 28 ahead of the precipitation chamber 30, where the CO.sub.2 in liquid phase suddenly cools the mixture and solidifies the wax.

[0033] In some embodiments, the injection of one or more CO.sub.2 co-streams are at a temperature below 0 degrees C. With one CO.sub.2 co-stream, the CO.sub.2 will be at least seven times the volume of the supercritical slurry stream and at 20 degrees C. or lower. That is, a ratio of CO.sub.2 to the slurry stream at this point is at least 7:1. The suddenly combined streams change the state of the initial CO.sub.2 slurry from supercritical to liquid. This phase change drops the wax components out of solution leaving the oil dissolved.

[0034] The wax is collected via gravity separation. Filtration may be added to the inside of the precipitation chamber 30 at its exit port as needed to ensure wax does not carry over into the separation chamber 48. A wax drain 40 may include a heater 42 or the system may be configured to pump steam into the precipitation chamber 30 to melt the solidified wax for retrieval from the bottom of the precipitation chamber 30. Multiple precipitation chambers may be set in a manifold to allow for the depressurization, heating, and draining of each as they fill with wax. In this way, the process can continue uninterrupted.

[0035] An output line 43 from the precipitation chamber 30 carries a mixture of CO.sub.2 and oil. The output line 43 includes a heat exchanger 44 that is configured to heat the mixture and a pressure regulator 46 that is configured to reduce pressure in the output line 43.

[0036] The separation chamber 48 receives CO2 and oil from the output line 43, where the CO.sub.2 is heated by the heat exchanger 44 to be in a gas phase, and where the oil then separates from the CO.sub.2. That is, when the pressure regulator 46 drops the pressure (e.g., to 1000 psi), the CO.sub.2 is no longer supercritical. The oil is in liquid form and heated so does not solidify and is not sticky. As such, the oil flows to the bottom of the separation chamber. The CO.sub.2 is in gas phase and flows out the top naturally, and is cooled back into liquid phase at a downstream heat exchanger. Multiple separation chambers 48 may be lined up in series to accommodate a series of smaller pressure drops on the stream's progress toward a lower pressure (e.g., 1000 psi). This allows for not only the specific separation of chemical species by pressure change, but the inclusion of filter media to remove components such as color bodies.

[0037] In some embodiments, the oil-CO.sub.2 solution is heated once again to 93 degrees C. to compensate for heat loss due to expansion, preventing clogs in the next step. Solution pressure is dropped through the pressure regulator 46, e.g., to 1000 psi, precipitating the oil without wax contaminants.

[0038] The CO.sub.2 is cooled by a downstream heat exchanger 50, e.g., to 4 degrees C., and the CO.sub.2 is returned to the CO.sub.2 supply tank 14 ready to be recirculated.

[0039] The system may also include various temperature sensors, pressure relief valves, feedback loops, and other safety components to ensure safe and efficient operation.

[0040] The system of the described embodiments utilizes CO.sub.2 in various phases along with temperature and pressure variations and various chambers to effectively and efficiently separate wax and oil from a sorghum slurry.

[0041] While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.